I've spoken to the TA today, to check if they were able to find the ZQ operated flights for redemptions. Apparently, they had no issue finding every flight.

I was advised that they believe it might be a bug with the website and app, since they're able to see them without issues. They've filed a report internally for an investigation.

In the meantime, the TA or PSL agents should be able to book these flights, or itineraries involving these.